Field of the Invention
The invention relates to a method of producing three-dimensional, selectively metallized parts, and three-dimensional, selectively metallized part.
The metallization of plastics using the electrodeposition technique enables the product to be completely metallized without additional measures. However, for most applications only partial metallization of the product is desired. There are various options for selective metallization. For example, a product can be injection-molded in two steps using two different plastics (two-component injection molding), in which case one plastic is metallizable and the other plastic is not metallizable. In that case, first of all a part is injection-molded from one plastic, and the part is then placed into a mold and completed by the injection molding of the other plastic. If the product is then metallized using a specific method, one plastic is metallized and the other is not metallized. Selective metallization can also be achieved by using light-sensitive resists. In this case, the entire product is initially provided with a thin, conductive metal layer by means of a chemical process. Then, a photoresist is applied and a pattern is produced in the resist by selective exposure and development. This pattern is reinforced by electrodeposition, and the photoresist can then be removed. It is now possible to remove the initial layer in an etching process, so that what remains is the pattern which has been grown on. A further possibility for selective metallization is made possible by the use of lasers. In that case, after metallization of the entire surface, the undesired metal layers can be removed locally by laser ablation (see, Report on the 15th Ulm Meeting on May 6 and 7, 1993 in Neu-Ulm, Eugen G. Leuze Verlag, Saulgau, pages 114-20, A. F. P. M. van Veggel xe2x80x9cHaftfeste Metallisierung von technischen Kunststoffenxe2x80x9d [Strongly adhering metallization of industrial plastics]).
In a variant of the production of selectively metallized products by two-component injection molding, a first core-catalyzed plastic and a second non-core-catalyzed plastic are used. The fact that the seeds have already been admixed with the first plastic means that in this case there is no need for wet chemical seeding of the injection-molded part. The subsequent metallization in a chemical metal deposition bath then results in selective deposition of metal in those regions which consist of the core-catalyzed plastic.
It is accordingly an object of the invention to provide a selectively metallized three-dimensional part and a production method, which overcome the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which allows simple and economical selective metallization of the three-dimensional parts.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of producing three-dimensional, selectively metallized parts from electrically insulating material, which comprises the following method steps:
producing three-dimensional parts by two-component injection molding, the parts having first regions to be metallized formed of a first plastic and second regions that are not to be metallized formed of a second plastic;
seeding an entire surface of the part;
selectively removing the seeding in the second regions that are not to be metallized aided by a solvent in which the first plastic is at least substantially insoluble and in which the second plastic is at least substantially soluble; and
depositing metal by electroless metal deposition in the first regions that are to be metallized.
The invention is based on the discovery that seeding of the entire surface of parts produced by two-component injection molding can be selectively removed by a solvent. This solvent must not attack the first plastic used in the regions which are to be metallized while it should readily dissolve the second plastic used in the regions which are not to be metallized, so that the seeding is selectively removed again in these regions. Then, subsequent electroless deposition of metal results in selective metallization of the regions which consist of the first plastic, since seeding is still present in those regions.
In accordance with an added feature of the invention, the electrolessly deposited metal layers are reinforced by electrodeposition. Reinforced metallization of this nature is particularly expedient for conductor patterns.
In accordance with an additional feature of the invention, seeding in a palladium system allows particularly effectively catalyzed electroless metal deposition in the regions which are to be metallized.
In accordance with another feature of the invention, the seeding is selectively removed using lye solution as the solvent. In this case, the fact that a first group of plastics is resistant to lye while a second group of plastics is soluble in lye is exploited. According to further refinements, PA and PS are preferably used as the first plastic which is resistant to lye. Similarly, LCP, PEI, PET, and PBT are good candidates for the second plastic, which is soluble in lye. Solvents based on KOH or NaOH are preferably used for the selective removal of the seeding. It is thereby possible to use pure KOH and pure NaOH, as well as mixtures of solvents which contain KOH or NaOH as the crucial component.
In accordance with a further feature of the invention, the seeding is selectively removed with acid as the solvent. In this case, the fact that a first group of plastics is resistant to acid while a second group of plastics is soluble in acid is exploited. In a preferred group, LCP, PEI, PET or PBT is preferably used as the first plastic, which is resistant to acid. Similarly, PA or PS is preferably used as the second plastic, which is soluble in acid. Furthermore, solvents based on HCl or H2SO4 or mixtures of C3O3 and H2SO4 or mixtures of CCl3xe2x80x94COOH and H2SO4 are preferably used for the selective removal of the seeding. It is thereby possible to use substantially pure HCl or pure H2SO4, or solvent mixtures which contain HCl or H2SO4 as the crucial components.
With the above and other objects in view there is also provided, in accordance with the invention, a three-dimensional, selectively metallized part which in the metallized regions consists of a first plastic and in the non-metallized regions consists of a second plastic. The first and second plastics have particular properties which are defined by the solubility in a predetermined solvent. The first plastic is at least substantially insoluble in a predetermined, specific solvent, while the second plastic is at least substantially soluble in the same solvent. For example, the first plastic is able to withstand lye, while the second plastic is soluble in lye. However, the first plastic may also be able to withstand acid while the second plastic is soluble in acid. These materials properties allow selective removal of seeding in lye or in acid during the production of the three-dimensional, selectively metallized parts.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a process for producing three-dimensional, selectively metallized parts, and three-dimensional, selectively metallized part, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.